Service feature table (no cache)

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Display a feature layer from a service using the no cache feature request mode.

screenshot

Use case

ServiceFeatureTable supports three request modes, which define how features are requested from the service and stored in the local table. The feature request modes have different performance characteristics. Use no cache in scenarios where you always want the freshest data.

How to use the sample

Run the sample and pan and zoom around the map. With each interaction, new features will be requested from the service and displayed on the map.

How it works

  1. Set the ServiceFeatureTable::setFeatureRequestMode property of the service feature table to FeatureRequestMode::OnInteractionNoCache before the table is loaded.
  2. Add the table to the map using a FeatureLayer.

Relevant API

  • FeatureLayer
  • FeatureRequestMode::OnInteractionNoCache
  • ServiceFeatureTable
  • ServiceFeatureTable::setFeatureRequestMode

About the data

This sample displays a Pool permit feature layer in Riverside, California, displaying which parcels do not have pool permits.

Additional information

In no cache mode, features are automatically populated from the service for the visible extent. Each time the user pans and zooms, features are downloaded for the visible extent. Features are still cached in a local geodatabase for display, but the cache will always be populated with the latest data after navigation.

NOTE: No cache does not guarantee that features won't be cached locally; feature request mode is a performance concept unrelated to data security.

Tags

cache, feature request mode, performance

Sample Code

ServiceFeatureTableNoCache.cppServiceFeatureTableNoCache.cppServiceFeatureTableNoCache.hServiceFeatureTableNoCache.qml
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// [WriteFile Name=ServiceFeatureTableNoCache, Category=Features]
// [Legal]
// Copyright 2016 Esri.

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// http://www.apache.org/licenses/LICENSE-2.0

// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// [Legal]

#ifdef PCH_BUILD
#include "pch.hpp"
#endif // PCH_BUILD

#include "ServiceFeatureTableNoCache.h"

#include "Map.h"
#include "MapQuickView.h"
#include "FeatureLayer.h"
#include "Basemap.h"
#include "SpatialReference.h"
#include "ServiceFeatureTable.h"
#include "Viewpoint.h"
#include "Envelope.h"
#include <QUrl>

using namespace Esri::ArcGISRuntime;

ServiceFeatureTableNoCache::ServiceFeatureTableNoCache(QQuickItem* parent) :
  QQuickItem(parent)
{
}

ServiceFeatureTableNoCache::~ServiceFeatureTableNoCache() = default;

void ServiceFeatureTableNoCache::init()
{
  qmlRegisterType<MapQuickView>("Esri.Samples", 1, 0, "MapView");
  qmlRegisterType<ServiceFeatureTableNoCache>("Esri.Samples", 1, 0, "ServiceFeatureTableNoCacheSample");
}

void ServiceFeatureTableNoCache::componentComplete()
{
  QQuickItem::componentComplete();

  // find QML MapView component
  m_mapView = findChild<MapQuickView*>("mapView");
  m_mapView->setWrapAroundMode(WrapAroundMode::Disabled);

  // Create a map using the topographic basemap
  m_map = new Map(BasemapStyle::ArcGISTopographic, this);
  m_map->setInitialViewpoint(Viewpoint(Envelope(-13075816.4047166, 4014771.46954516, -13073005.6797177, 4016869.78617381, SpatialReference(102100))));

  // Set map to map view
  m_mapView->setMap(m_map);

  // create the feature table
  m_featureTable = new ServiceFeatureTable(QUrl("https://sampleserver6.arcgisonline.com/arcgis/rest/services/PoolPermits/FeatureServer/0"), this);

  // set the feature request mode
  m_featureTable->setFeatureRequestMode(FeatureRequestMode::OnInteractionNoCache);

  // create the feature layer using the feature table
  m_featureLayer = new FeatureLayer(m_featureTable, this);

  // add the feature layer to the map
  m_map->operationalLayers()->append(m_featureLayer);
}

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